Self-cleaning tubular screen

ABSTRACT

A self-cleaning tubular screen adapted for dewatering or classifying particulates which embodies a slotted construction to provide a self-cleaning V-Slot that enlarges in the outward radial direction. The support rods for the tubular screen are located on the inner periphery of the tubular screen and attached to the wide face of wedge-shaped wire so as to preclude any interference with the slot opening. In a preferred arrangement the support rods are spiralled in order to enhance or improve particulate flow longitudinally through the screen.

United States Patent [72] Inventor David M. Likness Des Plaines, Ill. [21] Appl. No. 787,708 [22] Filed Dec. 30, 1968 [45] Patented Feb. 9, 1971 [73] Assignee Universal Oil Products Company Des Plaines, III. a corporation of Delaware [54] SELF-CLEANING TUBULAR SCREEN 2 Claims, 12 Drawing Figs.

[52] 0.8. CI 210/4911, 166/231 [51] Int. Cl 801d 29/22 [50] Field ofSearch 210/497.1, 4971-1, 498; 209/393, 395,407; 166/231, 232, 233

[56] References Cited UNITED STATES PATENTS 765,182 7/1904 King 210/497.l 866,560 9/1907 Basye 166/231 2,046,458 7/1936 Johnson 166/231 2,342,913 2/1944 Williams et a1. 166/233 2,690,265 9/ 1 954 Bixby 209/395X 2,942,730 6/1960 Fontein 209/393X 3,229,815 1/1966 Mathewson 209/270X FOREIGN PATENTS 477,621 1/1928 Germany 209/393 969,759 7/1958 Germany 292/323 218,036 7/ 1924 Great Britain 209/393 Primary Examiner-Samih N. Zaharna fl ilflnf Examiner- C. M. Ditlow Anorneys-James R. Hoatson, Jr. and Philip T. Liggett ABSTRACT: A self-cleaning tubular screen adapted for dewatering or classifying particulates which embodies a slotted construction to provide a self-cleaning V-Slot that enlarges in the outward radial direction. The support rods for the tubular the screen.

SELF-CLEANING TUBULAR SCREEN This invention relates to an improved form of self-cleaning screen for use in separating fluids from solid particulates. More specifically, this invention relates to a self-cleaning tubular screen formed by helically winding a wedge-shaped wire about a plurality of support rods and attaching same thereto in a manner to provide for radial outward flows. In other words, the cross-sectional area of the resulting continuous V-slot increases in the outward radial direction to give a self-cleaning effect when the flow of material initiates from the center of the tubular screen. The screen is susceptible to being rotated about its longitudinal axis so as to centrifugally force the material introduced into its interior, I radially outward. In a preferred form, the support rods may be spiralled so as to help effectuate longitudinal flow of the material introduced into the screen.

It is recognized that wedge-form separation screens are known and are used in various services such as well screens, vibrating or shaker screens, ore classifiers, and the like. Screens of tubular shape also have been used in a rotating action to centrifugally force a fluid'from slurry materials. However, it is to be noted that tubular screens of the self-cleaning type are generally fabricated to accommodate out-to-in flows. If an in-to-out flow screen is tobe manufactured, it is generally fabricated as an out-to-in flow screen and then reformed in a reverse manner in order to have the V-slot increase in an outward radial direction. This procedure is, of course, expensive and generally prohibitive.

It is thus a principle object of this invention to provide for an in-to-out flow tubular screen, suitable for rotation, having the benefit of a self-cleaning, but inexpensive construction. An alternative object, is to provide for an in-to-out flow screen construction that has support rod means that can aid in the positive movement of particulates in the longitudinal direction. 7 I

Broadly, this invention is a self-cleaning tubular screen comprising a plurality of spaced-apart longitudinal support rods and a wedge-shaped wire wound helically about said support rods and attached thereto, said wedge-shaped wire forming a resulting continuous V-slot of increasing cross-sectional area in the outward radial direction.

The means by which this type screen can be fabricated is generally known and is described in Johnson patents, US. Pat. Nos. 2,046,457; 2,046,458; 2,046,459; 2,046,460 and 2,046,461. Summarizing, these patents cover the apparatus and process whereby a wedge-shaped wire is helically wound about support rods and spot welded at each junction of wire and rod. The welding operation is described as an electrical resistance weld that fuses the two pieces together, the wire sinking into the rod some predetermined distance.

In most instances, the screen of this invention will be used for a flow or slurry of material to be directly introduced into the interior of the tubular screen. The fluid part of the slurry would be drawn off and thusly separated from solid particulates through the continuous slot by means of gravity, by means of maintaining a pressure differential between the interior and the exterior surfaces of the screen, or by means of rotational force; the particular means, however, not being a subject of this invention. In the simplest embodiment, the longitudinal flow of slurry is effectuated by maintaining the screen at a slope.

The solid particulates contained in the slurry of material are prevented from slogging in the continuous V-slot because the narrowest part of the V-slot is at the entry point on the interior periphery of the screen, and there is no depressed zone to permit particle bridging effects. Even in the event that a particulate would temporarily catch itself at one point of the slot, other particulates would tend to free it because of the continuity of the V-slot. v

A preferred embodiment makes use of the support rods as a means of establishing the flow of the particulates longitudinally through the screen. In other words, the support rods may be slightly spiralled so that when the screen is rotated, the

rods will drive the slurry of materials longitudinally forward. In an alternative application of this embodiment where rotation is not utilized, these spiralled support rods will enhance screening efficiency by changing initial longitudinal flow to circular flow, thereby increasing the contacted slot area. The resulting circular flow will also drive the fluid and finer materials through the slotted opening. In this embodiment, the preferred cross-sectional shape of each; of the support rods is substantially rectangular, thereby giving them a cross-sectional profile more likely to effect flow.

In this present invention, as previously noted, the novelty is in the winding of the wedge-shaped wire initially around the support rods to form the V-slot with a cross-sectional area increasing in the outward radial direction. However, the difficulty in obtaining such a result is manifested in the form of an at tachment of the wide face of the wedge-shaped wire to the support rods, as contrasted with the present conventional practice, which requires a weld to take place at the apex or smaller side of the wedge. If conventional wedge-shaped bars are used and a weld were to bemade at the wide part or base section of the wedge, the continuous feature of the resulting V-slot would be broken. Clogging would more likely take place, and any classification operations would be interferred with. Thus, preferably, a novel cross-sectional profile for the wedge-shaped wire is used as one means of fabricating the present in-to-out flow screen. This novel profile includes a ridge means along the central portion of the wide face of the wire, which may be used to assist in effectuating a weld to the longitudinal support rods; however, it is not intended to limit the ridge means to any one shape or cross section. Any shape chosen should be large enough to take a weld at the junction of a support rod and also have the dimensional requirements to prevent the weld from disturbing the edge of the wire.

The support rods will generally be equally spaced around the inner periphery of the tubular screen but may be spaced in any desirable manner. If the rods are not to be used to establish longitudinal flow through the screen, most probably they will be made parallel to the longitudinal axis of the screen. Also, the cross-sectional profile of the support rods may be of most any shape but consideration must be made in order to facilitate a strong weld. Round, oval, square, rectangular and all possible combinations may be considered probable cross-sectional profiles. In choosing a proper shape, the overall strength of the screen must be taken into account, in addition to the strength of the weld.

When the support rods are used as means of establishing flow, consideration must also be given to the area exposed to the particulate flow. It is for this reason that the dimension of the inner and outer sides of the cross-sectional area of the support rods will generally be made smaller than the dimension of the two adjacent sides. Again consideration must be given to the strength of weld and to the overall strength of the screen in establishing a proper cross-sectional profile.

Reference to the accompanying drawing and the following description will serve to more fully illustrate the design and construction of the various embodiments of the present invention, as well as to assist in pointing out. advantageous features in connection therewith.

DESCRIPTION OF DRAWING FIG. 1 is a schematic longitudinal elevational view of the one embodiment of the tubular screen with the slot formed to increase in area radially outwardly.

FIG. 2 is the schematic end view of the embodiment of FIG. 1.

FIG. 3 is a schematic perspective type of view of an embodiment in which the longitudinal support rods are spiralled.

FIGS. 4a, 4b, 4c, 4d and 4e are end views of various crosssectional areas of the support rods.

Referring now particularly to FIGS. 1 and 2 of the drawing, there is shown a tubular screen i formed by having a wedgeshaped wire 2 wound helically around a plurality of spacedapart longitudinal support rods 3. The wire 2 is wound in such a way so to form a continuous slot 4; however, because of the wedge shape of wire 2, the slot 4 increases in cross-sectional area in a radial outward direction. This feature provides a selfcleaning-type slot. Longitudinal support rods 3 are shown equally spaced around the inner periphery of the screen I and parallel to the longitudinal axis of the screen. The wedgeshaped wire is welded to the support bars at each junction 5.

This embodiment is susceptible to known manufacturing practices which have been described under the aforementioned US. Pat. Nos. 2,046,457; 2,046,458; 2,046,459, 2,046,460 and 2,046,461. Also, as set forth hereinbefore, the operation describes an apparatus and process by which a wire similar to wire 2 is wound around support rods similar to rods 3. The two are pressed together at their junction and welded through an electrical resistance means.

The wedge wire of these earlier patents was wound with the thin part or apex of the wedge abutting the support rods. This present invention reverses the wedge wire and changes its shape and also discloses spiral support rods, all to be hereinafter described.

'5 he embodiment of FIGS. 1 and 2 the tubular screen I is adapted to receive a slurry of materials to the open interior zone 6. The fluid in the slurry can be drawn off through the continuous slot 4 via suction, gravity, or centrifugal means. The power means for effectuating the suction or for effectuating the rotation of the tubular screen is not shown but may be provided in any conventional manner. Also, the screen can be supported at a slope to establish flow of slurry from the inlet to outlet of interior zone 6.

Another embodiment is illustrated in the partial perspective drawing shown in FIG. 3. In this embodiment, the tubular screen 7 is formed by the winding of a continuous wedgeshaped wire 8 around a plurality of spaced-apart longitudinal support rods 9. The longitudinal rods 9 are not parallel to the longitudinal axis of the tubular screen 7, but are spiralled as schematically shown. The amount of spiral that can be maintained will necessarily depend upon the requirement of overall screen strength. The spiraling of the longitudinal support rods 9 may be established in different manners.

One possible method is to first manufacture the screen with parallel support rods as shown in FIGS. 1 and 2 and then subject the tubular screen to a twisting force at a elevated temperature, whereby one end is turned relative to the other end. Strength considerations must be taken into account, of course, whenisubjecting a tubular screen to a twisting force.

Another possible method spirals the support rods during the actual turning and welding operation. The operation of forming screens as covered in the heretofore mentioned patents describes a turning of the longitudinal support rods with both the lead and opposite ends turning at the same rate. However, if the lead end of the machine on which the support rods are attached were turned at a slightly faster or slower rate than the opposite end, the longitudinal rods would form a spiral. The amount of spiral could be programmed by changing the relative speeds of rotation.

In the embodiment of FIG. 3, rotation is the preferred media to transmit a force upon the slurry that is received into the interior zone 1 1. Rotation of the screen 7 about its longitudinal axis will centrifugally force fluids contained in the slurry through the continuous slot 10, and in addition, will force the slurry longitudinally through the zone 11.

On the other hand, when the screen is used as a stationary classifier or drier, the embodiment of FIG. 3 will increase the screening efficiency of the slots it) by forcing the slurry of material contacting them into a circumferential direction. Thus, the slot area that the material will contact is increased, and the fluid is forced radially through the slots.

The movement of slurry is dependent upon the amount of spiral the rods 9 make. Movement will be effected to a greater extent with a more pronounced spiral. Also involved in effecting movement is the cross-sectional shape of the support rods 9 themselves. In other words, to increase the effect of the spiralled rods, the inside and outside dimensions l2, l3, 14 of the cross-sectional profile of the support rods will be made substantially smaller than the dimensions of the adjacent sides l5, l6, 17 as shown in FIGS. 40, 4b and 40.

FIGS. 4a, 4b, 4c, 4d and 4e show various alternative crosssectional profiles of the longitudinal support rods than can be used for various embodiments of the tubular screen. The wedge-shaped wire 18 is shown schematically in each FIG. to indicate where attachment would take place at the junction of support rods and wire. Also shown is a slight sinking or embedment 24 of the various support rods 19, 20, 21, 22 and 23 into the wire 18 which takes place when the junction is subjected to the pressure of electrical resistance welding and is thus a characteristic of the method of fabrication. Support rods in FIGS. 40, 4b and 40, as heretofore mentioned, are particularly adaptable for use in that embodiment containing FIG. 2. By illustrating these various profiles it is, of course, not

the intention to limit the choice of design to those shown.

In FIGS. 50, 5b, 5c and 5d there are shown various alternative cross-sectional profiles of the wedge-shaped wire used to form the continuous slot. A support rod 25 is schematically shown in each instance to indicate where attachment would occur between wound wire and support rod means. Again the sinking or embedment 26, characteristic of the method of fabrication, is shown. The profiles of the wires 27, 35, 37 and 38 are shown as a simple wedge; however, this should not be a limiting factor with respect to this invention since other wedge shapes are also contemplated within the scope of the improvement.

FIG. 5a illustrates the profiles of a wedge-shaped wire without the novel ridge means. It can be seen that if wire 27 is helically wound about a plurality of support rods 25, a V-slot 28 of increasing cross-sectional area in the outward radial direction 29 will be formed; however, there will be welding irregularities and a resulting nonuniform slot. To be self-cleaning and uniform the opening 30 of the V-slot 28 must be uninterrupted, i.e. if the wedge-shaped wire is merely shaped as shown in FIG. 5a, then weld irregularities would form along- To provide for an uninterrupted opening, a ridge 34 is incorporated into the profile, as shown on rod 35 of FIG. 5b.

This ridge 34 will most likely be continuous over the circumferential length of the rod 35, but alternatively, may be broken and only occur where needed for attachment purposes. The

ridge 34 serves as a contact for support rod 25. At this contact point a welding operation is possible without disturbing the edge 36 consequently leaving an uninterrupted opening 37.

Other possible shapes of ridges are shown in FIGS. 5c and 5 d but should not be considered as limiting designs. The important considerations in shaping each of these ridges are strength of weld designed and the prevention of disturbances along the edge 36.

Although I have described my invention with a certaindegree of particularity it is understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed. 1 v i lclaim:

l. A self-cleaning tubular screen adapted for rotation comprising a series of interior support rods radially equidistant from the longitudinal axis of said screen, said rods being of spiral configuration from end to end, a wedge-shaped wire helically wound about and externally of said support rods, said wedge-shaped wire forming a resulting continuous V-slot opening of increasing cross-sectional area in the outward radial direction, said wedge-shaped wire having ridge means on the base thereof facing said support rods, said ridge means providing an open area upon each side of said wire thereby presenting a smooth surface along said wire after welding thereof, whereby to assure uniformity of said opening, said rods projecting radially inward of the inner circumference defined by said wedge-shaped wire, whereby upon rotation of said screen particulate .flow is effectuated therethrough.

2. The tubular screen of claim 1 further characterized in that the cross section of said support rods are such that the dimension of the outer and inner sides of the cross section thereof is to be substantially smaller than the dimension of the two adjacent sides of said cross section whereby to facilitate particulate flow, longitudinally, through said tubular screen. 

2. The tubular screen of claim 1 further characterized in that the cross section of said support rods are such that the dimension of the outer and inner sides of the cross section thereof is to be substantially smaller than the dimension of the two adjacent sides of said cross section whereby to facilitate particulate flow, longitudinally, through said tubular screen. 